Ist my.freenom.com sicher?

Terrible!Terrible! You write to their support line and don’t get an answer for TWENTY days. Due to that the domain is expired. If you get any problems with your domain while this spook is your registrar, you are not going to be able to fix it and will lose domain!

they've deleted my domain without further warning because there wasn't any reachable website for some weeks on it. (my old host went down for some weeks, and after I've got a new one once I knew he wouldn't come back up, I forgot to update my domains IPs because I've been mainly using mail) My support request via ticket was left unanswered for a week and then automatically closed BECAUSE it wasn't answered within a week... So they're closing my tickets because they didn't answer it in time? Doesn't make much sense... Nonetheless, if their system would actually allow me to re-register my domain as my "your domain got deleted" mail told me, I wouldn't have to open up a ticket in first place.

Having a FREE domain name does not give you the legal registrant rights. Freenom allows you to use your chosen domain name for a period of 1 to 12 months. If you do not renew your domain name in time, your registration will be cancelled. Free renewals of FREE domains are allowed in the last 15 days of each registration period. If your website is down for a prolonged period or if your content is unacceptable/not uploaded the domain will be cancelled. Your domain name might then become automatically available for other registrants to register either as a free or as a paid registration.